A family study of primary affective disorders is being performed. Data have been collected on 2535 relatives of 162 patients. Preliminary application of genetic models to the data suggested that recessive inheritance was more likely than dominant. Under this hypothesis, possible linkage of ABO blood group locus to affective illness was noted in the largest pedigree studied. Enzymes of monoamine metabolism were studied as possible genetic markers in pedigrees of affectively ill patients, but it was found that altered neither dopamine-beta-hydroxylase (DBH) nor catechol-O-methyltransferase (COMT) activities were associated with transmission of affective illness within pedigrees. Extensive data analyses will be performed this year.